1. Field of the Invention
The present invention relates to a checking apparatus for checking electric properties of array electrode substrates, for example used in checking electrodes in a LCD panel (liquid crystal display panel).
2. Related Background Art
There are known apparatus for measuring a potential of an electrode on a panel, utilizing the electro-optic effect (E-O effect). With the apparatus, an electro-optic probe (E-O probe) made of a material having the electro-optic effect, is brought into the vicinity of the electrode to cause an index change according to an electric field, a laser light beam is radiated onto the electro-optic probe, and a change of a polarization state of reflection-return light is detected, there by checking the potential of the electrode on the pane.
The conventional technology of such apparatus is described, for example in Japanese Laid-open Patent Application No. 64-9370, Japanese Laid-open Patent Application No. 64-18071 (first reference), Japanese Laid-open Patent Application No. 64-18072, Japanese Laid-open Patent Application No. 64-18073, Japanese Laid-open Patent Application No. 3-244141 (second reference), "IEICE TRANS ELECTRON., VOL. E76-C, NO. 1 JANUARY 1993, PP64-67" (third reference), and "IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. QE-22, NO. 1, JANUARY 1986, PP69-78, PP79-93."
Among these, the first reference describes the technique that can be utilized for measuring potentials of many electrodes in an array electrode substrate such as a liquid crystal display panel, in which a large electro-optic probe is used and a linerary polarized measurement laser beam is scanned, thereby enabling measurement of a two-dimensional potential distribution. Further, the second and third references describe techniques which can allow simultaneous measurement of potential distribution in an area including a lot of electrodes by guiding parallel light with some spread to an electro-optic modulator, instead of a finely focused light beam.